In pneumatic tires, different areas of a tread are generally used when traveling in a straight line and in a curved line. This may cause portions of the tread to be worn to different degrees depending on the travel conditions, resulting in biased wear. Some conventional pneumatic tires have a tread of an appropriate shape so as to reduce biased wear. In a pneumatic radial tire described in Patent Document 1 for example, aiming to make uniform distribution of contact pressure and contact length in the tread being in contact with the ground, the tread is formed to have a crown shape including three arcs of different curvature radii such that the curvature radii of the arcs and the lateral widths of the arcs all fall in appropriate ranges. This allows the tread to be worn uniformly along a crown width direction even when the vehicle travels under various conditions. Thus, the biased wear is reduced.    Patent Document 1: Japanese Patent Application Laid-open No. H9-71107